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Can I charge a single battery while the whole bank is being charge or discharge?

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  • Can I charge a single battery while the whole bank is being charge or discharge?

    HI,

    I am wonder if I can charge a single battery in the 48 volt 8 battery bank with a different charger while the whole bank either being charge or discharging? one of the battery on the negative end of the bank has less SG reading all the time and the little EQ I did won't correct the problem, I haven't try a long period EQ yet, so I wonder if when the bank is drain down to 70% SOC, can I charge the single battery while the whole bank is charging by the solar in the early morning? or should I disconnect the bank from service and charge that battery alone?

    Thanks

  • #2
    NO If you have 1 low battery, you should pull it out and charge it by itself. Otherwise, you are testing the insulation and isolation of a battery charger by offsetting it with 48V, and most of the time it works, but when it doesn't, it's real ugly.
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

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    • #3
      Ok,

      Do I have to actually disconnect the cable from the bank or just turn off the disconnect breaker take the bank off duty and connect the 6/12 volts charger to the low battery?
      Thank you.

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      • #4
        Originally posted by paulcheung View Post
        Ok,

        Do I have to actually disconnect the cable from the bank or just turn off the disconnect breaker take the bank off duty and connect the 6/12 volts charger to the low battery?
        Thank you.
        If you have a negative grounded bank, you will not, under the NEC, be required to have a disconnect on the - battery lead.
        If you do not open the - battery lead, all but the first battery will still have both its negative and its positive terminal as a different voltage than ground.
        This will cause problems if the battery charger has the negative lead grounded, or if the insulation of the secondary winding which is feeding the rectifier is not good enough tot withstand as much as 48 volts DC.
        SunnyBoy 3000 US, 18 BP Solar 175B panels.

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        • #5
          Thanks for the reply, the battery in question is the last one on the negative end of the bank. The disconnect breakers is installed on the positive cables, the two bank negative end share one cable but the positive ends has separate cables with separate disconnect.
          Maybe to be safe I just going to remove the interconnect cable on the positive side of the battery I going to charge? I don't have to disconnect the command negative end cable, do I?

          Thanks again.

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          • #6
            Originally posted by paulcheung View Post
            Thanks for the reply, the battery in question is the last one on the negative end of the bank. The disconnect breakers is installed on the positive cables, the two bank negative end share one cable but the positive ends has separate cables with separate disconnect.
            Maybe to be safe I just going to remove the interconnect cable on the positive side of the battery I going to charge? I don't have to disconnect the command negative end cable, do I?

            Thanks again.
            No, you do not have to disconnect the common negative wire at the - end of the battery stack. I would not bother to disconnect the top end of that single battery as long as the + end of the entire stack was disconnected.
            And depending on your loads, you might not even have to disconnect the + end.
            Just make sure that the charger you use is either negative ground or has an isolated output.
            SunnyBoy 3000 US, 18 BP Solar 175B panels.

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            • #7
              Ok thank you.

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